The Incredible Shrinking Man (1957)

Businessman Scott Carey and his wife are on vacation, off the California coast, when their boat runs into radioactive cloud. Scott is exposed to the cloud while is wife is inside the boat. At first everything appears to be okay but Scott starts various things: clothes nothing fitting, his wedding ring falling off, his height and weight continuing to diminishes. After many studies it's appearing he is continuing to shrink while also being exposed to many dangers.